The present invention relates to a proton-conductive polymer membrane as well as to a method for its manufacture.
Fuel cell systems are becoming more and more important with regard to the supply of voltage for mobile electric and electronic apparatus. For achieving commercially common voltages, several fuel cells are connected in series for the addition of individual voltages. With a planar fuel cell arrangement, this is realised by way of connecting several fuel cell units arranged in a plane in series. Each fuel cell unit on the cathode and anode side in each case has a gas distribution structure and a diffusion layer. These two reaction spaces are separated by a membrane electrode assembly (MEA). This is a proton-conductive polymer membrane which is catalytically coated in the region of the reaction spaces. A known arrangement for the series connection of fuel cell units is the so-called strip membrane fuel cell. With this, a transverse conductor structure penetrates through the plane of the membrane and by way of this connects the cathode side of a first fuel cell unit to the anode side of the adjacent fuel cell unit. However the leading of the transverse conductor through the plane of the membrane quickly leads to leakage (unsealedness) of the fuel cell system.
For an improved sealing and for reasons of manufacturing technology, it is therefore advantageous to separate the reaction spaces of the anode side from the cathode side by way of a continuous polymer membrane which however still needs to have a catalyst coating in the region of the reaction spaces.
Polymer membranes are known for this, which are catalytically coated in segmented regions. At the same time, the catalyst layers may be deposited on the polymer membrane in segments by way of roller deposition or hot pressing. With these mechanical deposition methods, minimum distances of several millimeters (about 3 mm) are necessary between the individual adjacent catalyst segments in order to achieve a clear separation of the individual segments from one another. Additional problems arise due to the fact that the membrane is heated or deformed on deposition (e.g. by way of hot pressing), and thus an exact positioning of the catalyst segment and membrane is rendered more difficult.
One basic disadvantage of the known polymer membrane with catalyst segments is thus that due to the large minimum distances between the catalyst segments which must be maintained, surface area remains unused, which thus is no longer available for voltage production, in miniaturised planar fuel cells.